+ mm-memblockc-fix-null-dereference-error.patch added to -mm tree

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The patch titled
     Subject: mm/memblock.c: fix NULL dereference error
has been added to the -mm tree.  Its filename is
     mm-memblockc-fix-null-dereference-error.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-memblockc-fix-null-dereference-error.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-memblockc-fix-null-dereference-error.patch

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------------------------------------------------------
From: zijun_hu <zijun_hu@xxxxxxx>
Subject: mm/memblock.c: fix NULL dereference error

It causes NULL dereference error and failure to get type_a->regions[0]
info if parameter type_b of __next_mem_range_rev() == NULL

Fix this by checking before dereferring and initializing idx_b to 0

The approach is tested by dumping all types of region via
__memblock_dump_all() and __next_mem_range_rev() fixed to UART separately
the result is okay after checking the logs.

Link: http://lkml.kernel.org/r/57A0320D.6070102@xxxxxxxx
Signed-off-by: zijun_hu <zijun_hu@xxxxxxx>
Tested-by: zijun_hu <zijun_hu@xxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/memblock.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff -puN mm/memblock.c~mm-memblockc-fix-null-dereference-error mm/memblock.c
--- a/mm/memblock.c~mm-memblockc-fix-null-dereference-error
+++ a/mm/memblock.c
@@ -994,7 +994,10 @@ void __init_memblock __next_mem_range_re
 
 	if (*idx == (u64)ULLONG_MAX) {
 		idx_a = type_a->cnt - 1;
-		idx_b = type_b->cnt;
+		if (type_b != NULL)
+			idx_b = type_b->cnt;
+		else
+			idx_b = 0;
 	}
 
 	for (; idx_a >= 0; idx_a--) {
_

Patches currently in -mm which might be from zijun_hu@xxxxxxx are

mm-memblockc-fix-null-dereference-error.patch

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